Energy recuperation system and method for construction equipment

Abstract

An energy recuperation system for construction equipment includes an actuator driving upward and downward operations of a work unit; an accumulator connected to the actuator; and a controller determining a predicted downward mode associated with the downward operation of the work unit, regulating a dischargeable lowest limit pressure of the accumulator to a target pressure corresponding to the predicted downward mode, and charging the accumulator having the dischargeable lowest limit pressure regulated to the target pressure with pressurized oil discharged from the actuator during the downward operation of the work unit to recuperate energy, and an energy recuperation method.

The invention claimed is: 
     
       1. An energy recuperation system for construction equipment, comprising:
 an actuator configured to drive an upward operation and a downward operation of a work unit; 
 an accumulator connected to the actuator; and 
 a controller configured to determine a predicted downward mode associated with the downward operation of the work unit, to regulate a dischargeable lowest limit pressure of the accumulator to a target pressure corresponding to the predicted downward mode, and to charge the accumulator having the dischargeable lowest limit pressure regulated to the target pressure with pressurized oil discharged from the actuator during the downward operation of the work unit such that an energy recuperation is achieved. 
 
     
     
       2. The system of  claim 1 , further comprising:
 a memory configured to store information associated with the predicted downward mode and the target pressure, and to be controlled by the controller, 
 wherein the predicted downward mode includes: 
 a first predicted downward mode where the work unit has a first downward acceleration force at the downward operation; and 
 a second predicted downward mode where the work unit has a second downward acceleration force at the downward operation, the second downward acceleration force being less than the first downward acceleration force, 
 wherein the target pressure includes: 
 a first target pressure; and 
 a second target pressure having a higher pressure level than the first target pressure, and 
 wherein the controller is configured to correspond the first predicted downward mode with the first target pressure, and to correspond the second predicted downward mode with the second target pressure. 
 
     
     
       3. The system of  claim 2 , further comprising:
 a hydraulic pump configured to supply the pressurized oil to the actuator; 
 an assist motor configured to assist an engine to drive the hydraulic pump; 
 an assist passage configured to connect the accumulator and the assist motor to each other; and 
 an assist valve disposed in the assist passage and configured to control supply of the pressurized oil charged in the accumulator to the assist motor through the assist passage, 
 wherein the controller controls opening/closing of the assist valve so that the dischargeable lowest limit pressure of the accumulator reaches the first target pressure or the second target pressure. 
 
     
     
       4. The system of  claim 2 , further comprising:
 a lower driving structure; 
 an upper swing structure on which the work unit is mounted; and 
 a swing module connecting the upper swing structure rotatably to the lower driving structure, 
 wherein the controller additionally charges the accumulator, which has been charged with the pressurized oil during downward of the work unit under the second target pressure, with pressurized oil discharged from the swing module while the swing module stops a swing operation. 
 
     
     
       5. The system of  claim 1 , wherein the accumulator includes a plurality of sub-accumulators having different initial pressures,
 wherein the controller charges a sub-accumulator, which has an initial pressure corresponding to the target pressure, of the sub-accumulators with the pressurized oil. 
 
     
     
       6. The system of  claim 1 , further comprising:
 a charge passage connecting the accumulator and the actuator to each other; and 
 a charge valve disposed in the charge passage, 
 wherein the controller regulates pressure of the pressurized oil to be supplied into the accumulator by controlling the charge valve. 
 
     
     
       7. The system of  claim 1 , further comprising a motion sensor configured to measure information about one of the upward and downward operations of the work unit,
 wherein the controller acquires upward/downward operation pattern information by analyzing information measured by the motion sensor and determines the predicted downward mode on the basis of the upward/downward operation pattern information. 
 
     
     
       8. An energy recuperation method for construction equipment, the method comprising:
 determining a predicted downward mode of a work unit; 
 regulating a dischargeable lowest limit pressure of an accumulator to a target pressure on the basis of the predicted downward mode; and 
 charging the accumulator having the dischargeable lowest limit pressure regulated to the target pressure with pressurized oil discharged from an actuator actuating the work unit during downward of the work unit to recuperate energy. 
 
     
     
       9. The method of  claim 8 , wherein the determining of the predicted downward mode of the work unit includes:
 referring to a memory storing information about the predicted downward mode and the target pressure, wherein the predicted downward mode includes a first predicted downward mode and a second predicted downward mode and the target pressure includes a first target pressure and a second target pressure having a higher pressure level than the first target pressure, 
 wherein the regulating of the dischargeable lowest limit pressure of the accumulator to the target pressure on the basis of the predicted downward mode includes: 
 setting the dischargeable lowest limit pressure to the first target pressure to correspond to the first predicted downward mode or setting the dischargeable lowest limit pressure to the second target pressure to correspond to the second predicted downward mode. 
 
     
     
       10. The method of  claim 9 , wherein the regulating of the dischargeable lowest limit pressure of the accumulator to the target pressure on the basis of the predicted downward mode includes:
 regulating opening/closing of an assist valve such that the dischargeable lowest limit pressure reaches the first target pressure or the second target pressure while the pressurized oil charged in the accumulator is discharged to an assist motor. 
 
     
     
       11. The method of  claim 9 , wherein the accumulator includes a plurality of sub-accumulators having different initial pressures, and
 wherein the regulating of the dischargeable lowest limit pressure of the accumulator to the target pressure on the basis of the predicted downward mode includes: 
 selecting a sub-accumulator having an initial pressure corresponding to the first target pressure or the second target pressure from the sub-accumulators as an object to be charged with the pressurized oil discharged from the actuator. 
 
     
     
       12. The method of  claim 11 , wherein the selecting of the sub-accumulator having the initial pressure corresponding to the first target pressure or the second target pressure from the sub-accumulators as an object to be charged with the pressurized oil discharged from the actuator includes:
 making some of the sub-accumulators be objects to be charged by selectively opening/closing selection valves disposed for the sub-accumulators, respectively. 
 
     
     
       13. The method of  claim 9 , wherein the accumulator includes a plurality of sub-accumulators having different initial pressures,
 wherein the charging of the accumulator having the dischargeable lowest limit pressure regulated to the target pressure with pressurized oil discharged from the actuator actuating the work unit during downward of the work unit to recuperate energy includes: 
 sequentially charging the sub-accumulators with the pressurized oil discharged from the actuator such that the dischargeable lowest limit pressure of the accumulator reaches the first target pressure and the second target pressure with an interval. 
 
     
     
       14. The method of  claim 9 , wherein the determining of the predicted downward mode includes:
 selecting one of the first predicted downward mode and the second predicted downward mode as the predicted downward mode on the basis of work input from an operator through a work selector. 
 
     
     
       15. The method of  claim 9 , wherein the first predicted downward mode is a mode where the work unit is turned down with a first downward acceleration force and the second predicted downward mode is a mode where the work unit is turned down with a second downward acceleration force less than the first downward acceleration force. 
     
     
       16. The method of  claim 15 , further comprising:
 acquiring upward/downward operation pattern information by analyzing one of upward and downward operations of the work unit, 
 wherein the determining of the predicted downward mode of the work unit includes: 
 determining the predicted downward mode as one of the first predicted downward mode and the second predicted downward mode on the basis of the upward/downward operation pattern information. 
 
     
     
       17. The method of  claim 16 , further comprising:
 determining a starting time to charge the accumulator on the basis of the upward/downward operation pattern information. 
 
     
     
       18. The method of  claim 15 , further comprising:
 acquiring upward/downward operation pattern information by analyzing one of upward and downward operations of the work unit, 
 wherein the acquiring of the upward/downward operation pattern information by analyzing one of upward and downward operations of the work unit includes: 
 acquiring upward operation pattern information by analyzing upward factor information associated with upward of the work unit. 
 
     
     
       19. The method of  claim 18 , wherein the upward operation pattern information includes one of a stroke value of the actuator, an operation amount of an operation lever for the actuator, operation time of the operation lever, and an upward acceleration value of the work unit. 
     
     
       20. The method of  claim 19 , wherein the determining of the predicted downward mode of the work unit includes:
 determining the predicted downward mode as the first predicted downward mode if the stroke value is larger than a reference stroke value, or determining the predicted downward mode as the second predicted downward mode if the stroke value is smaller than the reference stroke value.